After two decades of effort to devise satisfactory contraceptive methods which depend on metabolic control mechanisms (oral contraceptives and progestational inserts) or on intra-uterine mechanical disruption, i.e. intrauterine devices (IUD's); alternative methods which depend on barriers (diaphragms, condoms) and on topical application of spermicides or other contraceptives (intravaginal foams or suppositories) have not become obsolete, and are still in wide use. These methods attract considerable interest due to their safety, freedom from undesirable side effects, and relative accessibility, without the need for a physician's intervention. The present invention relates to compositions for, and methods of, contraception based on topical intravaginal application of spermicides or other antifertility agents which inhibit sperm function.
Present formulations for intravaginal application of sperm function inhibitors are designed to insure coverage of the entire vaginal vault with the active ingredient (usually a surfactant, and typically nonoxynol-9, a nonionic surfactant).
One method for intravaginal application comprises supplying the contraceptive composition in the form of a gel.
The preparation of aqueous gels employing as gelling agents polyoxyethylene-polyoxypropylene block copolymers is well known to those skilled in the art and is taught in several patents including U.S. Pat. Nos. 3,740,421, 3,748,276, and 3,749,465.
U.S. Pat. No. 4,368,186 discloses that compositions designed for intravaginal application containing polyoxyethylene-polyoxypropylene block copolymers in substantial amount, have unexpected inherent spermicidal properties.
While the form of application of the spermicide may be varied, such as, gel, foam, cream, or a suppository designed to disintegrate and spread by means of, for example, an effervescent dissolution process, all of these application methods are basically similar to barrier methods in that they depend in the final analysis, on the spermicide encountering and destroying all sperm which enter the vagina.
For this reason, the present formulations and method of application cannot be considered totally satisfactory solutions to the problem. If they succeed in coverage of the entire vaginal surface, they are inherently messy and unaesthetic. If they fail to do so, they are relatively ineffective; a particular problem with those formulations designed in the form of dissolving suppositories.
It is known in the prior art to apply gels from aerosol containers as can be seen by the following:
U.S. Pat. No. 3,751,562, issued Aug. 7, 1973, to Nichols, discloses an aerosol gel formulation employing an oxyethylated fatty alcohol, mineral oil, iodine and water.
U.S. Pat. No. 4,293,542, issued Oct. 6, 1981, to Lang et al, discloses aerosol formulations which can be an aqueous gel containing oxyethylated fatty alcohols and a gel-forming agent and, as an essential component, a pyridine derivative. Another aerosol gel composition is disclosed in U.S. Pat. No. 4,001,391.
While it is known in the art to apply gel compositions by the use of aerosol-type containers, filling an aerosol container with a gel presents problems.
British No. 1,444,334 discloses an aerosol gel composition which may be employed as a shaving cream and which contains as a gelling agent a polyoxyethylene-polyoxypropylene block copolymer. An essential component of the composition is a water-soluble soap. This patent is concerned with the problem of expelling a gel from an aerosol container and particularly avoiding cavitation around the dip tube. Accordingly, the compressed gas or liquified gaseous propellant is required to be substantially insoluble in the gel so that it can act in the manner of a piston to force the gel from the container without cavitation. Aerosol gel compositions are also described in U.S. patent application Ser. Nos. 513,439; 524,985; 525,147 and 525,148.